Ouch! How Brexit may hit UK millionaires and billionaires

The U.K.'s wealthiest residents are poorer following last month's Brexit vote and will likely face further financial bad news, an international wealth consultancy warned on Monday.

"With the majority of HNWIs (high-net worth individuals) in the U.K. (14.3 percent) owing their wealth to the financial services industry, the billions that have been wiped off markets recently would have directly hurt the pockets of many HNWIs," WealthInsight said in a report.

"Moreover, the storm has not yet passed for HNWIs with investments in certain macro funds which have revealed deep losses," the consultancy added.

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WealthInsight defines high-net worth individuals as those with wealth of $1 million or more, excluding their primary residence.

The U.K.'s 15 wealthiest citizens lost a collective $5.5 billion in the stock market rout the day after the Brexit vote, according to Bloomberg. Britain's richest person, Gerald Grosvenor, led the decline with a loss of $1 billion, followed by Topshop owner, Philip Green, Charles Cadogan and Bruno Schroder, the news wire said.

One sore point for the wealthy in the wake of the referendum may be a delay in the publication of new rules on "non-doms" — the tax status awarded to many foreign-born wealthy people, said WealthInsight. A delay will add to uncertainty in the run up to the new rules coming into force in April 2017, it said.

In addition, luxury spending may decline — even if luxury assets flourish, according to the consultancy.

"Having seen prices plateau recently — partially in anticipation of the referendum — the same areas are now looking more attractive to HNWIs from overseas as the sterling devalues against their own currencies, notably the U.S. dollar," WealthInsight said.

Other benefits could include lighter-touch financial regulation than that currently imposed by the European Union and a boost to billionaire exporters like James Dyson if the decline in sterling continues, it added.

Whatever happens, London's lure for the rich will not diminish, WealthInsight said, noting the city has the most individuals per capita who are worth $30 million or more, excluding their primary residence.

"London's superior education standards and quality of life will continue to be as much an appeal to migrating HNWIs as its financial prowess. The capital's strong judicial system is already being used by foreign billionaires to settle disputes in their home countries, while its world class culture and education attracts many with families," it said.